EP0743769A2 - Système de réseau en boucle synchrone - Google Patents

Système de réseau en boucle synchrone Download PDF

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Publication number
EP0743769A2
EP0743769A2 EP96107912A EP96107912A EP0743769A2 EP 0743769 A2 EP0743769 A2 EP 0743769A2 EP 96107912 A EP96107912 A EP 96107912A EP 96107912 A EP96107912 A EP 96107912A EP 0743769 A2 EP0743769 A2 EP 0743769A2
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EP
European Patent Office
Prior art keywords
squelch
signal
path
order path
misconnection
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP96107912A
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German (de)
English (en)
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EP0743769B1 (fr
EP0743769A3 (fr
Inventor
Masataka c/o NEC Corp. Goto
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NEC Corp
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NEC Corp
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Publication of EP0743769A3 publication Critical patent/EP0743769A3/fr
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Publication of EP0743769B1 publication Critical patent/EP0743769B1/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/08—Intermediate station arrangements, e.g. for branching, for tapping-off
    • H04J3/085—Intermediate station arrangements, e.g. for branching, for tapping-off for ring networks, e.g. SDH/SONET rings, self-healing rings, meashed SDH/SONET networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
    • H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
    • H04J2203/0028—Local loop
    • H04J2203/0039—Topology
    • H04J2203/0042—Ring
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
    • H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
    • H04J2203/0057—Operations, administration and maintenance [OAM]
    • H04J2203/006—Fault tolerance and recovery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
    • H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
    • H04J2203/0089—Multiplexing, e.g. coding, scrambling, SONET

Definitions

  • This invention relates to a synchronous ring network system, and more particularly to, a synchronous ring network system in which a plurality of nodes are connected through a synchronous ring network to form a bidirectional line-switched ring(BLSR) system.
  • BLSR line-switched ring
  • a conventional synchronous ring network system comprises a plurality of nodes connected through a synchronous ring network, each of the plurality of nodes comprising multiplexing/demultiplexing means in which a TU signal which corresponds to a lower-order path signal is multiplexed to give an AU signal which corresponds to a higher-order path signal and the AU signal is demultiplexed to give the TU signal, higher-order path overhead processing means for conducting a production/termination control of a higher-order path overhead, lower-order path squelch means for squelching the TU signal, and higher-order path squelch means for squelching the AU signal.
  • the misconnection in higher-order path overhead is occurred since the AU squelch is released when completing the TU squelch at the termination node where the misconnected TU path is terminated.
  • the misconnection occurred in higher-order path overhead due to the releasing of AU squelch causes the disagreement of the path trace function, thereby failing to save a TU path which can be saved by the insertion of the AIS signal which responds to the disagreement.
  • the misconnection of F2 byte is occurred to reduce the reliability.
  • a synchronous ring network system comprises a plurality of nodes connected through a synchronous ring network, each of the plurality of nodes comprising multiplexing/demultiplexing means in which a TU signal which corresponds to a lower-order path signal is multiplexed to give an AU signal which corresponds to a higher-order path signal and the AU signal is demultiplexed to give the TU signal, higher-order path overhead processing means for conducting a production/termination control of a higher-order path overhead, lower-order path squelch means for squelching the TU signal, and higher-order path squelch means for squelching the AU signal, characterized in that each of the plurality of nodes further comprises:
  • the occurrence of the misconnection in a higher-order path overhead caused by protection switching and the unnecessary action from the detection of trouble can be prevented since the release of AU squelch is simultaneously conducted with the misconnection avoiding control of higher-order path overhead after completing TU squelch at the termination node where a misconnected TU path is terminated.
  • the misconnection avoiding control can be applied only to the byte which needs higher-order path overhead misconnection avoiding control.
  • FIG.1 shows a conventional system for preventing misconnection in the SDH(synchronous digital hierarchy) device.
  • a transmission signal T in and a reception signal T out are lower-order TU(tributary unit) signals in BLSR(bidirectional line-switched ring) system.
  • the lower-order TU signals of number N(N is a positive integer) are multiplexed/demultiplexed according to multiplexing/demultiplexing rules for SDH.
  • the lower-order path is generally defined as VC-11,12,3,2 and a higher-order path is generally defined as VC-4, where VC means a "virtual container”.
  • VC means a "virtual container”.
  • the higher-order path is referred to as "VC-4 path”.
  • a VC-4 path overhead processing unit 13 conducts the production/ termination of J1 byte, B3 byte, C2 byte, G1 byte, F2 byte, H4 byte, Z3 byte, Z4 byte and Z5 byte which are VC-4 path overhead bytes and also conducts a trouble detection and an action accompanied therewith in the receiving side.
  • An AU-4 pointer processing unit 12 conducts the production/interpretation of an AU-4 pointer and also conducts the detection of pointer trouble and an action accompanied therewith in the receiving side.
  • the "AU-4" pointer stands for "Administrative Unit - 4" pointer which points the top position of the VC-4.
  • “An administrative unit” is a combination of a payload and an AU pointer in a SDH frame, which provides an adaptation between a higher-order path layer and a multiplex section layer.
  • a TU squelch controller 15 squelches a transmission TU signal T in of each lower-order path.
  • the TU squelch control signal b from a BLSR controller 11 provides the controlling of squelch.
  • TU stands for "Tributary Unit” which is a combination of a payload and a TU pointer, which provides an adaptation between a lower-order path layer and a higher-order path layer.
  • the lower-order path is referred to as a TU path which comprises the payload section and the pointer section
  • the higher-order path(VC-4) is referred to as a AU path(AU-4 path) which comprises the payload section and the pointer section.
  • An AU squelch controller 16 squelches a transmission AU signal A out of each higher-order path.
  • the AU squelch control signal a from the BLSR controller 11 provides the controlling of squelch.
  • the BLSR controller 11 conducts APS(automatic protection switching) protocol processing of BLSR, protection switching control, searching for misconnection path caused by the protection switching, production of control signals a and b for AU squelch control and TU squelch control when a misconnection path is searched by the misconnection searching etc.
  • the TU squelch controller 15 When the TU squelch controller 15 receives a TU squelch request by the TU squelch control signal b, it converts the transmission TU signal into a TU path AIS(alarm indication signal) signal to work TU squelch. Also, when the AU squelch controller 16 receives an AU squelch request by the AU squelch control signal a, it converts the transmission AU-4 signal into a AU-4 path AIS signal to work AU squelch.
  • FIGS.2 and 3 an example of misconnection caused by the protection switching of a BLSR system for carrying traffic through a lower-order path(hereinafter referred to as "TU access") will be explained.
  • FIG.2 shows a normal state
  • FIG.3 shows a protection switching state.
  • TU path-i is laid on channel No.1 between node 1 and node 2
  • TU path-j is laid on channel No.1 between node 2 and node 3
  • TU path-1 is laid on channel No.1 between node 4 and node 1
  • TU path-m is laid on channel No.2 between node 1 and node 3 through node 2.
  • AUG(AU group number) including each TU path is common.
  • VC-4 path overhead is terminated at each node.
  • FIG.3 illustrates the case that node 2 is in trouble and nodes 1 and 3 are under protection switching.
  • nodes 1 and 3 are called switching nodes.
  • the TU path-m is saved by the protection switching, but the TU path-i and TU path-j are in misconnection due to the protection switching.
  • the VC-4 path overhead to be terminated between nodes 1 and 2 and VC-4 path overhead to be terminated between nodes 2 and 3 have been terminated between nodes 1 and 3, which is the wrong termination state.
  • FIGS.4 to 6 illustrate the squelch control method for preventing the misconnection in which the composition shown in FIG.3 is exemplified.
  • the squelch control is conducted by the insertion of a path AIS signal.
  • FIG.4 shows a state that AU squelch control is conducted at the switching nodes 1 and 3.
  • FIG.3 shows a state that the AU squelch is conducted and TU squelch control is conducted at the termination nodes where a misconnected TU path is terminated.
  • FIG.6 shows a state that the AU squelch control is released and only the TU squelch control is conducted.
  • the AU squelch control corresponds to the insertion of AU-4 path AIS signal to AUG including the misconnected TU path
  • the TU squelch control corresponds to the insertion of TU path AIS signal to the misconnected TU path.
  • the squelch control is conducted such that the AU squelch which is simultaneously carried out with the protection switching at a switching node is carried out as the first step and the states shown in FIG.4, 5 and 6 are in turn transferred not to cause the transient misconnection. These three steps are carried out triggered by the change in contents of K1 and K2 bytes which are APS bytes used for APS protocol communication between nodes.
  • FIG.7 a synchronous ring network system in the preferred embodiment will be explained in FIG.7, wherein like parts are indicated by like reference numerals as used in FIG.1.
  • the BLSR controller 11 conducts APS(automatic protection switching) protocol processing of BLSR, protection switching control and searching for a misconnection path, and it judges the misconnection of the VC-4 path overhead when the AU squelch is released and produces control signals a and b for AU squelch control and TU squelch control, respectively when a misconnection path is searched and further produces a VC-4 path overhead squelch control signal c for the misconnection avoiding control of the VC-4 path overhead.
  • the multiplexing/demultiplexing processing unit 14 multiplxes/demultiplexes TU signals T in , T out of number N(N is a positive integer) according to multiplexing/demultiplexing rules for SDH.
  • the VC-4 path overhead processing unit 13 conducts the production/ termination of J1 byte, B3 byte, C2 byte, G1 byte, F2 byte, H4 byte, Z3 byte, Z4 byte and Z5 byte which are VC-4 path overhead bytes and also conducts a trouble detection and an action accompanied therewith in the receiving side. Also, to the VC-4 path overhead byte which is previously set as a misconnection avoiding object by a VC-4 path overhead misconnection avoiding byte setting signal s, it stops the trouble detection and the action accompanied therewith in the receiving side when it receives the misconnection avoiding request through a VC-4 path overhead squelch control signal c from the BLSR controller 11.
  • the production of the misconnection avoiding byte may be stopped and a predetermined fixed value may be sent out.
  • a VC-4 path overhead squelch controller 17 which will be explained below, is not necessary.
  • the AU-4 pointer processing unit 12 conducts the production/interpretation of an AU-4 pointer and also conducts the detection of pointer trouble and an action accompanied therewith in the receiving side.
  • the TU squelch controller 15 When the TU squelch controller 15 receives a TU squelch request by the TU squelch control signal b, it converts the transmission TU signal into a TU path AIS(alarm indication signal) signal to work TU squelch. Also, when the AU squelch controller 16 receives an AU squelch request by the AU squelch control signal a, it converts the transmission AU-4 signal into a AU-4 path AIS signal to work AU squelch.
  • the procedure of the squelch control will be explained.
  • the conventional procedure of the squelch control for TU access comprises the three steps as shown in FIG.4, 5 and 6, the procedure of the invention includes an additional step for avoiding the VC-4 path overhead misconnection in the third step as shown in FIG.6.
  • the flow charts in FIGS.8 and 9 show mainly switching nodes 1 and 3.
  • nodes 1 and 3 adjacent to node 2 detect the SF(signal failure) state which is a ring switch request on the span to node 2(step 101).
  • nodes 1 and 3 send out an APS byte according to the APS protocol to node 2(step 102).
  • the APS byte sent from node 1 is shown in FIG.10B
  • the APS byte sent from node 3 is shown in FIG.10C.
  • FIGS.10A to 10E show APS bytes for the APS protocol processing, in which FIG.10A illustrates contents thereof.
  • the APS byte comprises K1 byte and K2 byte.
  • the K1 byte comprises "BRIDGE REQUEST CODE” which means a request level and "DESTINATION NODE IDENTIFICATION” which means the number of a transmitted node.
  • the K2 byte comprises "SOURCE NODE IDENTIFICATION” which means the number of a transmitting node, "L(long)/S(short)” which shows the distinction between a long path and a short path and "STATUS" which shows the state of switch and bridge.
  • the long path means a path contrary side of the span where a switch request is occurred
  • the short path means a path on the span where a switch request is occurred.
  • nodes 1 and 3 are sending the ring switch request, a response from the long path is waited(steps 103, 104).
  • both nodes 1 and 3 expect to receive the response from node 2, but node 1 receives the ring switch request from node 3 and node 3 receives the ring switch request from node 1.
  • the trouble in node 2 is recognized(step 105).
  • nodes 1 and 3 of switching nodes conduct a misconnection search for AU squelch control(step 106). With reference to FIGS.11 to 14, the processing of the misconnection search will be explained below.
  • a squelch table which shows that each path is connected between a node and another node is previously set. From the squelch table and the trouble node number obtained from APS byte, which path is misconnected is decided.
  • FIGS.11 to 14 are examples of the squelch tables which are previously set in nodes 1 to 4, which are applicable to the case of the BLSR system shown in FIG.2.
  • the squelch table to each AUG(AU group) number, information of an ADD node number, a DROP node number and whether a TU path is included is set on WEST(which is the side of a node adjacent to its node in the direction of CW) and EAST(which is the side of a node adjacent to its node in the direction of CCW) sides.
  • the ADD node number means an ADD node number of a time slot signal with AUG number n of a signal input to WEST/EAST side.
  • the DROP node number means an DROP node number of a time slot signal with AUG number n of a signal input to WEST/EAST side.
  • Whether a TU path is included means whether a TU path is included in AUG number n, i.e., it shows whether or not a TU access exists. If the TU access exists, it means that the squelch table of TU level as shown to the right side in FIGS.11 to 14 exists. The contents of the TU level squelch table are defined similarly as the above.
  • the switching nodes 1 and 3 search whether or not the ADD/DROP node number includes "2" in the squelch tables(in FIGS.11 and 13) of their own nodes.
  • the ADD/DROP node number includes "2”
  • the time slot is dealt to be misconnected.
  • AU squelch is conducted to the channel of AUG number 1(step 107) and switch and bridge control is simultaneously conducted(step 108).
  • FIG.10D The state that the step 106 is completed is shown in FIG.4.
  • FIG.10E The APS bytes in FIGS.10D and 10E are produced such that only "IDLE” in FIGS.10B and 10C is replaced by "BR & SW" which shows the state that bridge and switch control is conducted.
  • the above AU squelch is conducted by the AU squelch controller 16 through a control signal a from the BLSR controller 11 to insert the AU-4 path AIS signal.
  • each node conducts a misconnection search for TU squelch control(step 110).
  • the misconnection search is conducted using the squelch tables shown in FIGS.11 to 14.
  • "2" is searched in the TU level squelch table.
  • the misconnected TU path is decided to be laid on the channel TU No.1.
  • nodes 1 and 3 wait a response from the long path(step 111, 112). Thereafter, by receiving a APS byte, the fact that the status of the APS byte is changed from "IDLE” to "SW & BR" is confirmed(step 113) and TU squelch control is conducted(step 114).
  • the TU squelch is conducted by the TU squelch controller 15 through the control signal b from the BLSR controller 11 to insert the TU path AIS signal.
  • the misconnection avoiding control of the VC-4 path overhead which is an object of AU squelch release is conducted(step 115) and AU squelch release control is then conducted(step 116).
  • AU squelch release control is then conducted(step 116).
  • This is conducted such that the BLSR controller 11 of the SDH device which corresponds to the switching nodes 1 and 3 sends a misconnection avoiding request through the VC-4 path overhead squelch control signal c to the VC-4 path overhead squelch controller 17 and VC-4 path overhead processing unit 13 and simultaneously sends an AU squelch release request to the squelch controller 16.
  • a byte(a part of each byte of a VC-4 path overhead) which is previously designated by the VC-4 path overhead misconnection avoiding byte setting signal s becomes an object of the squelch.
  • the production and termination of its byte are stopped while in the VC-4 path overhead squelch controller 17 the fixed value "1" is set to all contents of the byte.
  • the production of the above byte may be stopped and a predetermined fixed value may be sent out therefrom.
  • the VC-4 path overhead squelch controller 17 is not necessary.
EP96107912A 1995-05-17 1996-05-17 Système de réseau en boucle synchrone Expired - Lifetime EP0743769B1 (fr)

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Application Number Priority Date Filing Date Title
JP7117581A JP2616486B2 (ja) 1995-05-17 1995-05-17 同期網リングネットワークシステム
JP11758195 1995-05-17
JP117581/95 1995-05-17

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EP0743769A2 true EP0743769A2 (fr) 1996-11-20
EP0743769A3 EP0743769A3 (fr) 1998-12-02
EP0743769B1 EP0743769B1 (fr) 2004-08-11

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EP (1) EP0743769B1 (fr)
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DE (1) DE69633091T2 (fr)

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JP3259126B2 (ja) 1995-09-26 2002-02-25 富士通株式会社 リング伝送システム及び該システムのスケルチ方法
JP3775859B2 (ja) * 1996-07-05 2006-05-17 富士通株式会社 非同期（ｐｄｈ）サブネットワークを含む同期（ｓｄｈ）ネットワークにおけるパス・スイッチ・リング制御装置
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ITTO980323A1 (it) * 1998-04-15 1999-10-15 Alsthom Cge Alcatel Metodo e circuito per la rivelazione di disuguaglianze nei pacchetti d i identificazione di traccia in trame sdh.
US6269452B1 (en) * 1998-04-27 2001-07-31 Cisco Technology, Inc. System and method for fault recovery for a two line bi-directional ring network
GB2338370B (en) * 1998-06-09 2000-07-19 Plessey Telecomm Telecommunications system
US6355886B1 (en) * 1999-05-21 2002-03-12 Tycom (Us) Inc. Undersea trunk-and-branch logical ring networks
JP4215369B2 (ja) * 2000-02-09 2009-01-28 株式会社日立コミュニケーションテクノロジー ネットワーク用伝送装置およびネットワーク伝送システム
JP3790097B2 (ja) * 2000-12-04 2006-06-28 富士通株式会社 リングネットワークの局認識方法
JP4565751B2 (ja) * 2001-01-16 2010-10-20 富士通株式会社 伝送装置
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JP2616486B2 (ja) 1997-06-04
DE69633091T2 (de) 2005-07-28
US5737310A (en) 1998-04-07
EP0743769B1 (fr) 2004-08-11
DE69633091D1 (de) 2004-09-16
EP0743769A3 (fr) 1998-12-02
JPH08316979A (ja) 1996-11-29

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